In an electrophotographic image forming apparatus such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine or a printer-copier-facsimile multifunction machine, an electrostatic latent image formed on a surface of a photoreceptor body by electrically charging the photoreceptor surface and exposing the photoreceptor surface to light is developed into a toner image with a toner, and a developing roller is used for the development.
In order to suppress adhesion of the toner for prevention of reduction in image density, the friction on an outer peripheral surface of the developing roller is desirably reduced. For this purpose, an oxide film is generally formed in the outer peripheral surface by irradiating the outer peripheral surface with ultraviolet radiation as described, for example, in Patent Document 1.